1. Field of the Invention
The present invention relates to an electron-emitting device using surface conduction electron-emitting elements, and an image display apparatus in which the electron-emitting device is provided. Further, the present invention relates to an apparatus for production of the electron-emitting device.
2. Description of the Related Art
Conventional electron emission sources for emitting electrons are classified into two major types: hot-cathode devices and cold-cathode devices. The cold-cathode devices include FE (field emission) type, MIM (metal/insulator/metal) type, and surface conduction type. The FE type electron emission devices are, for example, disclosed in “Field Emission” Advance in Electron Physics, vol. 8, p. 89, 1956, by W. P. Dyke & W. W. Dolan and “Physical Properties of Thin-Film Field Emission Cathodes with Molybdenum” J. Appl. Phys., 475248, 1976, by C. A. Spindt. The MIM type electron emission devices are, for example, disclosed in “The Tunnel-Emission Amplifier”, J. Appl. Phys., vol. 32, p. 646, 1961, by C. A. Mead. The surface conduction electron emission devices are, for example, disclosed in “Radio Engineering Electron Physics”, 1290 (1965) by M. I. Elinson.
Electron-emitting elements of the above surface conduction type utilize the electron emission that is caused by flowing an electric current to a thin film formed with a small area on a substrate, the flow of the current being parallel to the film surface. Hereinafter, these electron-emitting elements and boards or other devices including the electron-emitting elements of this type are called the surface conduction electron-emitting devices.
The surface conduction electron-emitting devices that have been reported in the technical literature include those employing a SnO2 thin film proposed by M. I. Elinson, those employing an Au thin film (“Thin Solid Films”, vol. 9, p. 317, 1972, by G. Dittmer), those employing an In2O3/SnO2 thin film (“IEEE Trans. ED Conf.”, p.519, 1975, by M. Hartwell and C. G. Fonstad), and those employing a carbon thin film (“Shinku (Vacuum)”, vol.26, No. 1, p.22, 1983, by Hisashi Arai et al.).
FIG. 31 shows a configuration of a conventional electron-emitting device, which belongs to the above, surface conduction type.
As shown in FIG. 31, in the conventional electron-emitting device, a substrate 1, a pair of opposing electrodes 2 and 3, a conductive thin film 4, and an electron-emitting region 5 are provided. The thin film 4 is formed on the substrate 1 between the electrodes 2 and 3 through sputtering using an electron-emitting material. The thin film 4 is provided with a width “W′” that is approximately 0.1 mm. The electrodes 2 and 3 are formed on the substrate 1 to establish electrical connection. The electrodes 2 and 3 are provided with a distance “L1” that ranges from 0.5 mm to 1.0 mm.
Generally, in the electron-emitting devices, such as that shown in FIG. 31, the electron-emitting region 5 is formed by performing an energizing heat treatment, called “forming”, before effecting the electron emission. Specifically, a voltage is applied between the electrode 2 and the electrode 3 to energize the film 4 such that the film 4 is locally destroyed or deformed owing to the Joule heat. The applied voltage causes the electron-emitting region 5 to be held in a state of electrically high resistance, so that the resulting electron-emitting region 5 carries an electron-emitting function.
The state of electrically high resistance of the electron-emitting region 5 is given by a discontinuous state of the film 4 partly having cracks on the surface of the film 4. In the surface conduction electron-emitting devices, a voltage is applied to the high-resistance, discontinuous-state film 4 by using the electrodes 2 and 3 to flow the current to the surface of the film 4, so that the electrons are emitting from the electron-emitting region 5.
The surface conduction electron-emitting devices as mentioned above have the advantageous features that they have a simple structure, they are easy to manufacture, and a large number of electron-emitting elements can be easily arranged in a relatively large area of the thin film. Currently, electron beam sources or image display devices that utilize the surface conduction electron-emitting devices are under development.
For example, Japanese Laid-Open Patent Application Nos. 64-31332, 1-283749 and 2-257552 disclose an electron beam source in which a plurality of the surface conduction electron-emitting devices are arrayed in a matrix formation, and an image display device in which the surface conduction electron-emitting device is provided as the electron beam source.
Further, U.S. Pat. No. 5,066,883 discloses a surface conduction electron-emitting device for use in an image display device. In the image display device of the above document, the surface conduction electron-emitting device is provided as the electron beam source and a target of a fluorescent material is provided to emit a visible light from the portion of the target where an electron beam from the electron beam source hits.
However, a conventional production method for the surface conduction electron-emitting devices, such as those disclosed in the above documents, uses the vapor deposition method and the photolithographic etching method heavily. Hence, in the conventional production method, there are the problems that it requires a large number of manufacturing processes in order to arrange electron-emitting elements in a relatively large area of the thin film, and that the production cost is considerably increased.
In order to overcome the above problems, another production method for the surface conduction electron-emitting devices has been proposed. This production method uses an ink jet drop application device which applies drops of a source material to the substrate to form a conductive thin film in which the surface conduction electron-emitting devices are arranged. For example, U.S. Pat. Nos. 3,060,429, 3,298,030, 3,596,275, 3,416,153, 3,747,129 and 5,729,257 disclose such ink jet drop application devices. The above-mentioned production method makes it possible to arrange the electron-emitting elements in a relatively large area of the thin film without using the vapor deposition method or the photolithographic etching method. The above-mentioned production method has a potential that lowers the manufacturing cost and achieves good yields.
However, in the application of drops of the source material to the substrate in order to form the conductive thin film, which differs from the application of ink drops to the paper in the known ink jet printing, the problems, such as drop application conditions, drop forming conditions and substrate handling conditions, remain unresolved.
Further, in the above-mentioned production method using the ink jet drop application device, when producing the electron-emitting device, the ink jet drop application device applies the drops of the source material to the substrate and the production apparatus forms the conductive thin film in which the surface conduction electron-emitting devices are arranged. In the case of the ink jet printing, the paper can be easily transported to the image forming position where the discharge head is provided. Unlike the ink jet printing, it is necessary that the substrate is suitably attached to or removed from the production apparatus and accurately transported, and the problems of the substrate handling that are specific to the above production method remains.